State lawmakers behind Colorado’s push for increased high-density housing around transit hubs see trouble ahead: a lagging Regional Transportation District bus and train system. When they invited agency leaders to a transportation hearing at the Capitol this week to talk about it, RTD balked. This flummoxed lawmakers because they’ve been counting on tightly packed “transit-oriented communities” as the core of their approach to many of Colorado’s problems, including traffic congestion, climate-warming vehicle pollution and affordable housing for workers. “If we don’t have transit, the whole thing falls apart,” Rep.